I've always been fascinated by the description of the three sources of power in the Soviet Union (The Military, the KGB, and The Party), as described in the book "Inside The Soviet Army" by Victor Suvorov (actual name Vladimir Rezun) He describes how these three organizations would battle for power, where the other two would always prevent one from becoming all powerful. He described The Politburo as essentially neutral ground, where issues were hashed out, decided, etc.

My question is, is there some fairly simple analogous way to describe the actual US system, as opposed to how the system is described in a high school civics class? I think there is such a system, but it probably has more than three "legs"" it would include the rich business people, especially Wall Street types, the actual military, the secret agencies, the political parties (actually more or less the same), and the people, who do have some influence. Maybe a five-legged structure. Or maybe a six-sided structure, also including the press. Six "players" could also involve two triangles, which meet at a point, where the real decisions are made. Or they could meet at a line and form a rectangle. A triangle also has the property that any point is adjacent to the other two. The two triangles would be the gov't one (Political parties, military, secret agencies inc. military intelligence) and the private one, the rich, the press and the people. Can perhaps also be thought of three dimensionally (http://en.wikipedia.org/wiki/Platonic_solid). The 3D analogy to the triangle might be a tetrahedron, with the rich, the political class, the military, and the secret agencies.

I have linked to "Inside the Soviet Army", and have included an excerpt.

A triangle is the strongest and most rigid geometric figure. If the planks of a door which you have knocked together begin to warp, nail another plank diagonally across them. This will divide your rectangular construction into two triangles and the door will then have the necessary stability.
The triangle has been used in engineering for a very long time. Look at the Eiffel tower, at the metal framework of the airship Hindenburg, or just at any railway bridge, and you will see that each of these is an amalgamation of thousands of triangles, which give the structure rigidity and stability.
The triangle is strong and stable, not only in engineering but in politics, too. Political systems based on division of power and on the interplay of three balancing forces have been the most stable throughout history. These are the principles upon which the Union of Soviet Socialist Republics is built.
Enormous problems and difficulties are said to lie before the Soviet Union. But Soviet leaders have always been confronted by problems of considerable magnitude, from the very beginnings of Soviet power. Then, too, the collapse of the regime was thought to be inevitable. But it survived four years of bloody struggle against the Russian army; it survived the mutiny of the Baltic fleet, which had itself helped to bring about the Revolution; it survived the mass flight of the intelligentsia, the opposition of the peasants, the massive blood-letting of the revolutionary period, the Civil War, the unprecedented slaughter of millions during collectivisation, and endless bloody purges. It also withstood diplomatic isolation and political blockade, the starvation of scores of millions of those it enslaves and an unexpected onslaught by 190 German divisions, despite the unwillingness of many of its own soldiers to fight for its interests.
So one should not be in a hurry to bury the Soviet regime. It is still, fairly firmly, on its feet. There are several reasons for its stability-the scores of millions of corpses within its foundations, disinterested Western help, the reluctance of the free world to defend its own freedom. But there is one other most important factor which gives the Soviet regime its internal stability-the triangular structure of the state.
Only three forces are active in the Soviet political arena-the Party, the Army and the KGB. Each of these possesses enormous power, but this is exceeded by the combined strength of the other two. Each has its own secret organisation, which is capable of reaching into hostile countries and monitoring developments there. The Party has its Control Commission-a secret organisation which has almost as much influence inside the country as the KGB. The KGB is a grouping of many different secret departments, some of which keep an eye on the Party. The Army has its own secret service-the GRU-the most effective military intelligence service in the world.
Each of these three forces is hostile to the others and has certain, not unreasonable pretensions to absolute power but its initiatives will always fail in the face of the combined opposition of the other two.
Of the three, the Party has the smallest resources for self-defence in open conflict. But it has a strong lever at its disposal-the appointment and posting of all officials. Every general in the Army and every colonel in the KGB takes up his post and is promoted or demoted only with the approval of the Administrative Department of the Central Committee of the Party. In addition, the Party controls all propaganda and ideological work and it is always the Party which decides what constitutes true Marxism and what represents a deviation from its general line. Marxism can be used as an additional weapon when it becomes necessary to dismiss an unwanted official from the KGB, the Army or even the Party. The Party's right to nominate and promote individuals is supported by both the Army and the KGB. If the Party were to lose this privilege to the KGB, the Army would be in mortal danger. If the Army took it over, the KGB would be in an equally dangerous situation. For this reason, neither of them objects to the Party's privilege-and it is this privilege which makes the Party the most influential member of the triumvirate.
The KGB is the craftiest member of this troika. It is able, whenever it wishes, to recruit a party or a military leader as its agent: if the official refuses he can be destroyed by a compromise operation devised by the KGB. The Party remembers, only too clearly, how the KGB's predecessor was able to destroy the entire Central Committee during the course of a single year. The Army, for its part, remembers how, within the space of two months, the same organisation was able to annihilate all its generals. However, the secret power of the KGB and its cunning are its weakness as well as its strength. Both the Party and the Army have a deep fear of the KGB and for this reason they keep a very close eye on the behaviour of its leaders, changing them quickly and decisively, if this becomes necessary.
The Army is potentially the most powerful of the three and therefore it has the fewest rights. The Party and the KGB know very well that, if Communism should collapse, they will be shot by their own countrymen, but that this will not happen to the Army. The Party and the KGB acknowledge the might of the Army. Without it their policies could not be carried out, either at home or abroad. The Party and the KGB keep the Army at a careful distance, rather as two hunters might control a captured leopard with chains, from two different sides. The tautness of this chain is felt even at regimental and battalion level. The Party has a political Commissar in every detachment and the KGB a Special Department.

excerpt
In the centre of the triangle, or more accurately, above the centre, sits the Politburo. This organisation should not be seen as the summit of the Party, for it represents neutral territory, on which the three forces gather to grapple with one another.
Both the Army and the KGB are equally represented in the Politburo. With their agreement, the Party takes the leading role; the Party bosses restrain the others and act as peacemakers in the constant squabbles.
The Politburo plays a decisive part in Soviet society. In effect it has become a substitute for God. Portraits of its members are on display in every street and square. It has the last word in the resolution of any problem, at home or abroad. It has complete power in every field-legislative, executive, judicial, military, political, administrative, even religious.
Representing, as it does, a fusion of three powers, the Politburo is fully aware that it draws its own stability from each of these sources. It can be compared to the seat of a three-legged stool. If one of the legs is longer than the others, the stool will fall over. The same will happen if one of the legs is shorter than the others. For their own safety, therefore, the members of the Politburo, whether they come from the Party, the KGB or the Army, do everything they can to maintain equilibrium. The secret of Brezhnev's survival lies in his skill in keeping the balance between the trio, restraining any two from combining against the third.

One way to think about the US actual power structure, although probably over-complicated, is as an octahedron - two tetrahedrons joined together at a square/rectangle.

One tetrahedron would be the rich, the press, the people, and large political donors. The other would be the political class, the military, the secret agencies, and the defense contractors. They meet and hash things out at the square - which can be thought of as the high school civics version, with the three branches of gov't and the independent agencies/bureaucracies. The two points away from the intersection could be the people and the military. They have the least day-by-day influence but ultimately are the keys to what goes on.

The system has worked best, I think, when there is significant back-and-forth between the military and the people. They are also the purist/least corrupt.

Contrary to the ideas of the ancients who looked to all-powerful rulers, it seems that decentralization is actually best for fostering progress and for making a society resilient in the face of adversity. IMO the most critical failure of communism was the concentration of nearly all power in hands of the party. This creates a stovepipe that rewards political skills at the expense of all else leading ultimately to stagnation.

In an open society, power is somewhat free to shift to the people and organizations best adapted to the then current environment.

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Any metaphor will tear if stretched over too much reality.

I would say that neither the military nor the press are power structures. The military never has been, since the USA has never had a professional military, and it is completely dominated by civilian appointees. I don't see the military as having any real power.

The press used to be, but given that nearly all commercial press outlets in the USA are owned by a few corporate entities I think they are more a tool than a 'player'.

One aspect of the US power structure that too many outsiders (and not a few Americans) don't get is the ability of the Federal Courts to impact life. while the police are a galaxy of autonomous agencies, most if not all police powers and procedures stem from Federal case law, not statutes written by the legislative bodies.

Another major power bloc is the bureaucracies, both Federal and state. although headed by political appointees, they exert a great deal of real power by men who remain in office far longer than politicians.

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Any man can hold his place when the bands play and women throw flowers; it is when the enemy presses close and metal shears through the ranks that one can acertain which are soldiers, and which are not.